1. Field of the Invention
This invention relates to a novel method and appratus for the filtration of suspended solids and soluble matter, from a liquid (i.e. dispersions or an emulsion). In particular, the invention relates to an improved method and apparatus having an internal filtrate collection chamber within the filter bed.
2. Description of the Prior Art
Filtration, which is the separation of solids and liquids into two mutually exclusive fractions, is desirable in many applications. These applications include, but are not limited to, the quality improvement of drinking water, liquid discharge from municipal and industrial wastewater treatment plants to the environment, and many chemical processes involving the separation of solids and liquids.
Such needs can most economically be met by physical separation techniques. Exemplary means for such separation include a wide variety of downflow filters compressing a bed of particulate filter material contained within a vessel have been proposed and implemented for this purpose. Each of these prior filters have depended upon fixed or rigid pervious retaining devices; for example, screens, porous plates, or other type of liquid-permeable device, to retain this bed of particulate filter material and entrapped solids in place, while allowing the filtered liquid to pass through the retaining device and exit the filter. Examples of such prior downflow filters are described in U.S. Pat. Nos. 4,060,484 to E. P. Austin Et al; and my pending patent application, Ser. No. 247,397.
One of the problems of downflow filters, having an internal filtrate collection chamber, is that the pervious retaining devices are subject to clogging and blockage, which gradually restricts the flow of filtered liquid into the the filtrate collection chamber, thereby impairing filter effectiveness and efficiency. This undesirable condition may be caused by, but is not limited to, biological growth, impingement of fine filter media within the openings of the retaining device, and chemical scaling formed within the openings of the retaining device.
Remedies for overcoming these and similar problems include the removal of the filter media at regular intervals to allow periodic access to scrub the retaining devices to remove flow restrictive debris from the retaining devices. In many cases, such retaining devices may require replacement incurring additional equipment cost. In each of the aforementioned remedies, the filter must be removed from service for the repair period. Most users of downflow filters would find it desirable to use a filter that does not have a pervious retaining device and its associated problems.